Method for operating an internal combustion engine, taking into consideration the individual properties of the injection devices

Abstract

A method for operating an internal combustion engine, in which fuel is injected using an injection device into a combustion chamber of a cylinder of the internal combustion engine, a fuel quantity to be injected being ascertained as a function of individual properties of the injection device, and in which functional monitoring is performed, in which an actual torque is ascertained on the basis of performance quantities of the internal combustion engine and monitored for a deviation from a permissible torque. The individual properties of the injection device are taken into consideration when ascertaining the actual torque, where the functional monitoring is improved.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a method for operating an internal combustion engine, in which fuel is injected using an injection device into a combustion chamber of a cylinder of the internal combustion engine, a fuel quantity to be injected being ascertained as a function of individual properties of the injection device, and in which functional monitoring is performed, during which an actual torque is ascertained on the basis of performance quantities of the internal combustion engine and monitored for deviation from a permissible torque. Furthermore, the present invention relates to a control unit for an internal combustion engine as well as a computer program for a control unit of this type.BACKGROUND INFORMATION[0002]Within the scope of typical operating methods, the actual torque actually delivered by the internal combustion engine is ascertained from various performance quantities of the internal combustion engine, such as an injection duration a...

AI Technical Summary

Benefits of technology

[0008]More precise ascertainment of the actual torque is thus possible, and smaller tolerance thresholds may be established for monitoring of the internal combustion engine using the actual torque, e.g., within the scope of a comparison of the actual torque with a permissible torque derived from the setpoint torque provided for the activation of the internal combustion engine, by which the monitoring is also improved because errors may be recognized more rapidly.

[0009]According to a very advantageous embodiment of the present invention, compensating values corresponding to the individual properties of the injection device are used when ascertaining the actual torque. For a specific injection device, for example, such compensating values indicate a deviation of a diameter of a nozzle opening from a value averaged statistically over multiple injection devices for the diameter of the nozzle opening and, in this way, with simultaneous knowledge of the statistically averaged value and the compensating value, allow the nozzle diameter of the injection device in question to be determined and thus to at least partially compensate for its tolerances, which are mostly related to manufacturing.

[0014]Another advantageous embodiment of the operating method according to the present invention is characterized in that the compensating values are transferred from functions which may be implemented outside the functional monitoring, in particular from an activation of the internal combustion engine. In this way, the compensating values do not have to be read out from an EEPROM or ascertained in another way in the functional monitoring, but rather may be copied directly from corresponding variables of functions responsible for the activation of the internal combustion engine, for example, by which resources of the control unit such as RAM, ROM, and runtime may be saved.

[0015]A further refinement of the method according to the present invention is characterized in that the transferred compensating values are subjected to a plausibility check, which may use theoretical maximum values and / or an injection pressure and / or an injected fuel volume. Increased reliability when ascertaining the actual torque is thus provided, which allows even more reliable functional monitoring of the internal combustion engine.

Problems solved by technology

However, the typical operating methods are sometimes very inaccurate with regard to ascertaining the actual torque which, inter alia, is to be attributed to a large scatter of the individual properties of the injection devices.

Images